title: Magna-field irradiation: physical considerations.
abstract: Magna-field radiotherapy in the form of total body, half body and total nodal irradiation is becoming increasingly prominent and involves dosimetric problems that are much more pronounced than they are for conventional field sizes. In this review of the physical considerations of magna-field irradiation, a number of possible alternate methods of producing large radiation fields are outlined, the basic beam dosimetry is reviewed and the factors producing dose variation in the patient are considered. Since the lung contains large regions of low density tissues and has a lower tolerance to radiation than most other tissues, special consideration is given to methods of dose determination and dose reduction to this organ. The question of accuracy in dose delivery is briefly discussed and the concept of delivering a radiation dose 'as precisely as readily achievable (APARA), technological and biological factors being taken into account' is introduced.
authors.affiliation: Ontario Cancer Institute, Princess Margaret Hospital, Toronto, Ontario, Canada.
authors.forename: J
authors.initials: J
authors.lastname: Van Dyk
mesh_terms: D004307:Dose-Response Relationship, Radiation; D017619:Hemibody Irradiation / Q000379:methods*; D006801:Humans; D008168:Lung / Q000528:radiation effects*; D015182:Lymphatic Irradiation / Q000379:methods*; D011832:Radiation Injuries / Q000517:prevention & control*; D011835:Radiation Protection; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D014057:Tomography, X-Ray Computed; D014916:Whole-Body Irradiation / Q000379:methods*